This page provides information to assist with the operation and maintenance (O&M) of photovoltaic (PV) systems. Key resources are provided for a deeper dive into the topics. Return to the Life Cycle of PV Systems landing page to explore more phases in this process.
It’s important to follow the Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems to ensure safe, efficient system performance and to complete preventive and pre-storm maintenance.
For information about creating an O&M plan, see the Prepare O&M Plan section, which can be applied to existing as well as new PV systems.
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Perform Preventive Operation and Maintenance
Preventive operation and maintenance are essential for long-term safety and performance.
Use a checklist like the Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems technical report when developing a plan.
General tips for operation and maintenance:
- Regularly monitor the site to prevent the build-up of debris. For electrical equipment, remove animal nests and other debris, ensure proper wire management, and replace plastic ties, which are more prone to premature failure.
- If severe weather or fire is likely, have a plan in place for pre-storm O&M and how to fund repairs.
- For third-party owned and insured systems, understand the weather events that are covered under the policy and if there is a cap to claim amounts, and be aware of exclusions. This is most likely not applicable for government agencies.
- Ensure proper information management of monitoring system. Archive important information such as passwords and essential files to prevent unnecessary downtime.
- Conduct electrical inspections after inverter nuisance tripping. When the system trips off, conduct an electrical inspection to check for ground faults. Do not just turn the system off and on, as this will likely not address the root problem.
Confirm PV System Performance
PV system performance can vary based on:
- Location-specific solar availability
- Daily solar availability due to weather patterns
- Module age and degradation rate (often about 0.5% per year according to the PV O&M Best Practices report)
- Severe weather events.
Monitoring systems should track performance over time and be able to report energy production hourly, daily, monthly, and annually since inception.
Check two key performance indicators regularly (monthly to annually, depending on the system size):
1. Performance Ratio
Performance ratio refers to the fraction of the expected power output when the plant is available (see IEC 61724). The performance ratio can be evaluated over any time period (instantaneously, monthly, annually). It is calculated as the ratio of actual production (measured by a production meter on the PV system) to model production, which is based on a computer model of the same measured solar resource and temperature data over the selected time period (considering the age of the system ).
Performance ratio = actual production/model production (%)
2. Availability
Availability refers to the percentage of time that the system is operational and capable of delivering power if the solar resource and the grid are both working (see IEC 63019). Availability is calculated from time-series data according to:
Availability = (1-downtime)/total time (%)
According to the U.S. General Services Administration (GSA) Operations and Maintenance Services of Government-Owned Solar PV Systems template, normal operating conditions occur when:
- A system is operating within 80% of its weather-corrected performance ratio. Performance evaluation by FEMP indicates that a performance ratio of 85% and availability of 95% should be achievable.
- System components meet required codes, standards and practices.
Inspection and Testing Procedures
The same template notes that the contractor should adhere to the following procedures for inspection and testing to establish normal operating conditions:
- Contractor performs inspection and testing
- Contractor submits baseline operating conditions report with recommended corrective services
- Contractor submits for government acceptance and approval to proceed with corrective services
- Contractor performs corrective services
- Contractor validates normal operating conditions have been achieved
- Contractor submits normal operating conditions report
- Contractor submits for government acceptance.
Calibration of meters, sensors, and other equipment is one way to ensure the accuracy of monitoring performance over the PV system’s lifetime. The frequency of calibration can depend on the system’s size or alternatively can be performed at a frequency based on the manufacturer’s specifications. The Operations and Maintenance Request for Proposal Template for Government-Owned Solar Photovoltaic Systems (for full and open O&M contracts) and GSA’s Operations and Maintenance Services of Government-Owned Solar PV Systems recommend calibration frequencies based on system size.
The same templates also specify the frequency that performance reports should occur, which also vary based on system size. The suggested performance report and calibration frequencies specified in the Operations and Maintenance Request for Proposal Template for Government-Owned Solar Photovoltaic Systems (for full and open O&M contracts) is listed here:
| PV System Size (kW) | Calibration Frequency | Performance Report Frequency |
|---|---|---|
| < 250 kW | Every 5 years | Biannually |
| 250 kW – 1,000 kW | Every 2-5 years | Quarterly or Biannually |
| 1,001 kW – 3,000 kW | Every 1-2 years | Quarterly |
| > 3,000 kW | Annually | Monthly |
For detailed specifics on performance data collection and archiving requirements, contractors should consult the “Data Frequency Intervals and Archive Length” table on page 16 of the Operations and Maintenance Request for Proposal Template for Government-Owned Solar Photovoltaic Systems. This table outlines the necessary frequency for collecting various operational data points and their required archive durations, with requirements varying based on the size of the photovoltaic system.
Finally, for a system that is underperforming, the contractor must adhere to the response times specified in the O&M plan. A template for the response times and site visit schedule is included on page 20 of the Operations and Maintenance Request for Proposal Template for Government-Owned Solar Photovoltaic Systems.
General management strategies for checking system performance include:
- Regularly check operational indicators (energy production meters, error messages on inverter faceplate).
- Consider subscribing to a monitoring service.
- Bundle the O&M of small systems together.
- Develop an O&M plan and budget.
- Plan ahead for repairs.
- Ensure adequately trained O&M staff, either by on-site maintenance training or by contracting O&M services to qualified professionals.
- Consider performance contracting to deliver O&M on a denomination of cents-per-kWh delivered.
- Regularly check O&M cost expenditures and ensure they are as expected.
- Optimizing Solar Photovoltaic Performance for Longevity
- Understanding Solar Photovoltaic System Performance: An Assessment of 75 Federal Photovoltaic Systems, FEMP Technical Report (2022)
- Operations and Maintenance Request for Proposal Template for Government-Owned Solar Photovoltaic Systems
- Operations and Maintenance Services of Government-Owned Solar PV Systems, FEMP Technical Report (2021)
- Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems, Technical Report (2018)
- Optimizing Solar Photovoltaic Performance for Longevity
Perform Pre-Storm Operation and Maintenance
Pre-storm operation and maintenance prepares systems for extreme weather and helps reduce risk.
General pre-storm O&M measures include:
- Ensure that the PV system site is clean and secure. Make sure key areas are clear of debris, such as sources of fire ignition or drains and flood control systems. Remove debris.
- Tie down loose material in and around arrays. Tie down or anchor HVAC and other in-use equipment.
- Conduct mechanical and electrical measures such as stowing, covering, properly enclosing, or otherwise protecting components when possible.
- Install an emergency power-down device for electrical circuits.
- Perform tightness checks on fasteners, racking systems, and other support systems.
- Waterproof access panels, electrical enclosures, conduit fittings and other components that may be susceptible to moisture damage where possible.
- Perform a torque audit of all fasteners.
- Set modules to stowed mode.
- Power off the system if possible.
- Power down components by opening breakers, fuses and switches.
- Prioritize system survival over production.
- If battery is attached, ensure it is fully charged.
Download Preparing Solar PV Systems Against Storms for a comprehensive pre-storm solar PV checklist.
General post-storm recovery includes:
- Dry and clean all electrical systems.
- Perform a torque audit of fasteners.
- Test for electrical faults in all systems.
- Replace all damaged electrical systems before energizing.
Measures for storm hardening (hurricanes and other severe weather) and their associated cost implications for ground mount and rooftop systems are summarized in the table below. These recommendations are adapted from Solar Photovoltaics in Severe Weather: Cost Considerations for Storm Hardening PV Systems for Resilience (2020), Preparing Solar Photovoltaic Systems Against Storms (2022), and Solar Photovoltaic Systems in Hurricanes and Other Severe Weather (2018).
| Measure | Benefit | Cost Implications |
|---|---|---|
| Properly torque fasteners and perform a torque audit. | Prevents loose fasteners and helps to secure critical system components. Increases survivability during storm. | Increased labor cost from audit. |
| Choose well-designed fasteners that pass Junker testing standards. | Helps fasteners to remain secure throughout their lifetime and prevent loose fasteners. | Subject to change due to availability, quantity ordered, vendor markup, and other factors that may influence the price a developer may pay. |
| Through bolt modules directly to underlying racking. | Prevents module from coming free of racking, increases clamp strength. | Requires twice as many fasteners and a longer installation time per fastener (increased labor time/cost). |
| Use marine-grade steel fasteners. | Prevents corrosion of fasteners, especially in coastal areas. | Cost to replace 18-8 grade bolts, nuts, and washers with 316-grade stainless steel hardware. |
| Select panels with appropriate resistance to wind loading (adequate front and back pressure). | Prevents module failure during high wind speed events. | Increased cost of a module with a higher pull (uplift) rating. |
| Use a three-framed rail system. | Increases system strength through providing more attachment points and more stability during high wind. | Requires 50% more materials (rails, clamps, bolts, nuts, washers) and added labor time for the “east-west” rails that support modules. |
| Use two driven steel pile supports. | Increases system stability. | Using two driven pile supports instead of one. |
| Use closed form frame elements. | Tubular or square supports are less likely to twist or deform during storms. | Higher weight and cost of frame support elements. |
| Use a wind calming fence. | Decreases the occurrence of strong winds on the system. | Material and labor costs to design, procure and install fence. |
| Use enclosures with integrated and contiguous rubber door seals and compression latches on all sides. | Prevent flooding and water saturation, electronic component replacement. | No cost premium for this measure, should be a standard feature included in design. |
| Install equipment on elevated pads (ground-mount only). | Reduce likelihood of water damage. | Installation cost of installing all electrical equipment on pads. Install equipment on 18-inch-deep square concrete pads. Baseline cost is nothing. |
| Ensure site has well-designed and maintained drainage systems, through vegetation planning, etc. | Prevent water and flood damage. | Varies by site and local conditions. Should be budgeted for in design and maintenance plans. |
- Preparing Solar Photovoltaic Systems Against Storms, Fact Sheet (2022)
- Solar Photovoltaic Systems in Hurricanes and Other Severe Weather, White Paper (2018)
- Solar Photovoltaics in Severe Weather: Cost Considerations for Storm Hardening PV Systems for Resilience, Technical Report (2020)
- Preparing Solar Photovoltaic Systems Against Storms, Fact Sheet (2022)
Execute a Post-Damage Recovery Plan
A PV failure mode is defined as disturbance or damage to one or multiple components of a PV system, which could result in risks such as a loss of power performance, faulty connections, inverter tripping, wire faults, and other potentially hazardous occurrences. Always budget for damage repair in a system’s O&M plan.
If your PV system has experienced a failure, proper recovery procedures can ensure efficient and cost-effective recovery of the system.
This section provides information and resources related to:
- How to render a system safe.
- System vulnerabilities along with their safety, performance, and financial risks.
- Corrective actions related to scoping repairs and their associated cost considerations.
How To Render a System Safe
The priority following a damage event is to render the system physically and electrically safe pending inspection, testing, and repairs. Generally, the best practices after a performance failure occurs are to:
- Shut down and disconnect the system.
- Secure the site for physical and electrical safety.
- Secure any loose items that may move or blow away in the wind.
- Shut down disconnects to isolate any damage from electrical hazard.
- Block public access to damaged areas (e.g., carports with loose PV modules overhead).
- Properly clear site of debris.
- Inspect and electrically test components to identify and diagnose problems.
- Undergo thermal, UV, or infrared imaging to identify hidden damage.
- Itemize components that are required to be repaired or replaced.
- Deploy a reserve account or pursue financial resources, hire contractors, and purchase replacement components.
- Repair, rebuild or replace damaged parts of the system.
- Fully recommission the system and return to service.
- Resume performance monitoring.
System Vulnerabilities and Corrective Actions
The 2021 PV System Owner's Guide to Identifying, Assessing, and Addressing Weather Vulnerabilities, Risks, and Impacts report presents several types of risks associated with vulnerable PV system components:
- Safety risks: Bodily harm to persons or property
- Performance risks: Underperformance or going offline for an extended period of time
- Financial risks: Avoidable costs such as those to repair, rebuild, or replace the PV system or PV system components.
System vulnerabilities can also be categorized by PV system component. Pages 14-16 of the 2021 PV System Owner's Guide to Identifying, Assessing, and Addressing Weather Vulnerabilities, Risks, and Impacts report categorize common system vulnerabilities by PV component and maps them to their safety, performance, and financial risk.
In this guide, vulnerabilities and their associated corrective actions are listed for each PV system component category. The relative safety, performance, and financial risks are categorized into highest, medium, and low risk. Corrective actions are also displayed and categorized by associated relative material and labor costs. More information can be found in the 2021 PV System Owner's Guide to Identifying, Assessing, and Addressing Weather Vulnerabilities, Risks, and Impacts report.
After damage has occurred, inspection and electrical testing is needed to itemize required repairs, and a cost estimate should be prepared to fix the damage and bring the system back into service. Costs to repair a system after damage has occurred depend on factors such as:
- Regional variation
- System size
- Array type (e.g., flat roof, pitched roof, ground mount—fixed tilt, ground mount—carport, ground mount—tracker)
- Difficulty of access to an array
- Extent of repair involved.
The technical report, Model of Operation-and-Maintenance Costs for Photovoltaic Systems, presents a PV O&M cost model which estimates total O&M costs, including administrative tasks, preventive O&M (such as inspection and cleaning), and corrective maintenance for failed component replacement.
According to this model, correcting normal day-to-day replacement of failed components accounts for 22% of annual maintenance cost for an example 200 kW rooftop system and 14% of maintenance cost for a 500 kW ground-mount system.
This cost model does not estimate the cost of severe storm damage, fire, or other hazards. Instead, it includes insurance as the single largest operating cost to represent cost associated with managing such hazard risk. For the 200 kW rooftop system, the cost model estimates insurance at 19% of annual maintenance cost and 21% for the 500 kW ground-mount example.
However, the federal government is self-insured. While insurance provides a fund to make repairs quickly and often includes business interruption insurance to pay for lost energy production, the federal government must access emergency O&M funds or seek appropriations to make repairs. These processes may take time and may not be an agency priority following a severe event.
As a result, many agencies pursue third-party ownership procurement methods, such as power purchase agreements or energy savings performance contract energy service agreements, rather than appropriations for PV projects, to benefit from performance guarantees and risk management. Regardless of procurement method, understanding available financial resources after a failure is important to assess what options may be available to responsible parties.
For more information on properly assessing and calculating cost to make improvements and take measures to prevent damage, refer to Section 7 of the PV System Owner's Guide to Identifying, Assessing, and Addressing Weather Vulnerabilities, Risks, and Impacts report. This section includes cost factors (typically ranging from approximately 0.5 to 1.9) to reflect costs of a “hardened system” compared to the “standard system” described in the report.
Table 15 of the PV System Owner's Guide to Identifying, Assessing, and Addressing Weather Vulnerabilities, Risks, and Impacts report summarizes financing options for agencies facing large repair costs (e.g., appropriations, integration with an O&M contract, combining with a current energy project, using a performance contract to have the PV system taken over by a contractor.)
PV System Life Cycle
You're on phase 3 of the PV System Life Cycle. Learn more about each phase and explore key resources: